Reported on 7 News and confirmed by Qantas and FR24, QF1 (depart SYD Monday 2 January 2023) diverted to Athens for a medical emergency.
Aircraft operating is VH-OQJ, which remains in ATH at this time. QF flight status page indicates a continuation to LHR early afternoon Wednesday 4 January local time (I assume, being medical rather than technical, that this will be OQJ).
Tuesday’s QF2 is scheduled to depart LHR mid-morning on Wednesday local time, which presumably will operate with VH-OQD which left SYD as QF1 on Tuesday 3 January.
Edit to add link:
https://7news.com.au/news/in-flight-...-c-9341816.amp